Panel lifespan: 25–35 years
Most solar panels carry a 25-year performance warranty guaranteeing at least 80% of original output at year 25. In practice, quality panels degrade at just 0.3–0.5% per year, meaning they'll still produce 85–90% of their rated power after 25 years.
Panels don't suddenly stop working at year 25. They continue generating electricity at gradually declining rates. Many systems installed in the 1990s are still running in 2026 — producing less than they did originally, but still earning their keep.
What actually degrades?
Several factors cause solar panel output to decline over time:
- Light-Induced Degradation (LID). Panels lose 1–3% in the first few weeks of operation as the silicon stabilises. This is a one-off drop, already factored into performance guarantees.
- Cell degradation. Gradual breakdown of the silicon cells reduces electron flow. Modern monocrystalline panels degrade at 0.3–0.5% per year — better than older polycrystalline models (0.5–0.8%).
- Microcracks. Thermal cycling (hot days, cold nights) can create hairline cracks in cells over decades. Leeds's moderate climate is actually gentler on panels than extreme heat/cold environments.
- Encapsulant yellowing. The clear EVA layer protecting the cells can yellow over 20+ years, slightly reducing light transmission.
Inverter lifespan: 10–15 years
The inverter — which converts DC from panels to AC for your home — is the component most likely to need replacing. String inverters last 10–15 years. Microinverters (one per panel) last longer: 15–25 years typically.
Budget £800–£1,500 for a replacement string inverter at year 12–15. This is the main ongoing cost of a solar system. See our maintenance guide for full servicing details.
Real-world data
A 2024 study by the National Renewable Energy Laboratory (NREL) analysed 54,500 solar installations across multiple countries and found a median degradation rate of 0.5% per year. UK-specific data from the Solar Trade Association shows similar results, with northern England systems slightly outperforming due to cooler operating temperatures.
In Leeds, a 4kW system installed today should still produce 2,700 kWh/year at year 25 (down from ~3,200 kWh). At 24.5p/kWh, that's still £660/year in savings — plus winter generation offsets.
Compare quotes from Leeds installers and ask about panel degradation warranties — top manufacturers guarantee 90%+ at year 25.